Frequency increasing sensor protocol in magnetic sensing

ABSTRACT

A magnetic sensor is configured to measure a magnetic field whose magnitude oscillates between a first extrema and a second extrema. The magnetic sensor includes a plurality of magnetic field sensor elements, each configured to generate a sensor signal in response to the magnetic field impinging thereon. The plurality of sensor elements are grouped into a first group from which a first measurement signal is derived and a second group from which a second measurement signal is derived, and the first measurement signal and the second measurement signal having a phase difference based on different phases. The magnetic sensor further includes a sensor circuit configured to receive the first measurement signal and the second measurement signal, and apply a signal conversion algorithm thereto to generate a converted measurement signal having an increased frequency with respect to the first measurement signal and the second measurement signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/686,307 filed Aug. 25, 2017, which is incorporated by reference as iffully set forth.

FIELD

The present disclosure relates generally to magnetic sensors, and, moreparticularly, to magnetic sensors configured to increase a frequency ofa sensor protocol and methods for implementing the same.

BACKGROUND

Today, vehicles feature numerous safety, body and powertrainapplications that rely on magnetic position and/or angle sensors. Forexample, in Electric Power Steering (EPS), magnetic angle sensors andlinear Hall sensors can be used to measure steering angle and steeringtorque. Modern powertrain systems can rely on magnetic speed sensors forcamshaft, crankshaft and transmission applications, along withautomotive pressure sensors, to achieve required CO₂ targets and smartpowertrain solutions.

In the field of speed sensing, a sinusoidal signal may be generated by amagnetic sensor in response to a rotation of a target object, such as awheel, camshaft, crankshaft, or the like. The sinusoidal signal may betranslated into pulses, which is further translated into a movementdetection or a speed output. Both anti-lock braking system (ABS)applications and transmission applications, for example, have a trendfor requiring more pulses per revolution for increased accuracy. In bothABS and transmission applications it is desired that the number ofpulses per revolution be increased by a factor 2, 4, or even higher.

In the field of position sensing, in a similar sense, sinusoidal signalsmay be used to calculate accurate angle information, for example, forsteering wheel position sensing. For position sensing, a higher degreeof resolution is desired.

Currently, higher accuracy requirements in speed sensing applicationsmay be realized with an increase of number of poles or teeth on a targetobject. However, the number of poles or teeth on a target object dependson the object diameter and, in general, there is a technical limit tothe minimum size of a single pole or tooth. In addition, the higher thenumber of pole pairs or tooth/notches, the higher the manufacturingcosts. Thus, increasing the numbers of poles or teeth relates in a tradeof between cost and accuracy. In addition, an increase in the number ofpoles or teeth may also increase bandwidth requirements.

Therefore, an improved sensing device without increasing the number orpoles or teeth of a sensing target may be desirable.

SUMMARY

Magnetic field sensors and sensing methods are provided.

Embodiments provide a magnetic sensor configured to measure a magneticfield whose magnitude oscillates between a first extrema and a secondextrema. The magnetic sensor includes a plurality of magnetic fieldsensor elements, each configured to generate a sensor signal in responseto the magnetic field impinging thereon. The plurality of sensorelements are grouped into a first group from which a first measurementsignal is derived and a second group from which a second measurementsignal is derived, and the first measurement signal and the secondmeasurement signal having phase difference of 90°. The magnetic sensorfurther includes a sensor circuit configured to receive the firstmeasurement signal and the second measurement signal, and apply a signalconversion algorithm thereto to generate a converted measurement signalhaving an increased frequency with respect to a frequency of the firstmeasurement signal and the second measurement signal.

Embodiments further provide a method for measuring a magnetic fieldwhose magnitude oscillates between a first extrema and a second extrema.The method includes generating a first measurement signal representingthe measured magnetic field; generating a second measurement signalrepresenting the measured magnetic field, wherein the first measurementsignal and the second measurement signal have a phase difference of 90°;and applying a signal conversion algorithm to the first measurementsignal and the second measurement signal in order to generate aconverted measurement signal having an increased frequency with respectto a frequency of the first measurement signal and the secondmeasurement signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described herein making reference to the appendeddrawings.

FIG. 1 is a block diagram illustrating a magnetic speed sensor accordingto one or more embodiments;

FIG. 2A is a graph showing an example of a sinusoidal waveform generatedby a magnetic speed sensor according to one or more embodiments.

FIG. 2B is a plan view of a magnetic encoder wheel used in speed sensingaccording to one or more embodiments;

FIG. 3A is a block diagram illustrating a magnetic angle sensoraccording to one or more embodiments;

FIG. 3B is a schematic diagram of X and Y sensor bridges of the magneticangle sensor illustrated in FIG. 3A;

FIG. 4A is a graph showing an example of a sinusoidal waveform generatedby a magnetic angle sensor according to one or more embodiments;

FIG. 4B is a plan view of a magnetic target using in angle sensingaccording to one or more embodiments;

FIG. 5 illustrates sinusoidal waveforms of a speed signal and adirection signal for one pole pair generated by a speed sensor accordingto one or more embodiments;

FIG. 6 illustrates absolute values of the sinusoidal waveforms shown inFIG. 5 according to one or more embodiments;

FIG. 7 illustrates a new speed signal waveform derived from the signalsshown in FIG. 6 according to one or more embodiments;

FIG. 8 illustrates a normalized signal of the triangular waveform shownin FIG. 7 according to one or more embodiments;

FIG. 9 illustrates normalized speed signals derived from the signalsshown in FIG. 7 according to one or more embodiments;

FIG. 10 illustrates a normalized signal of a triangular waveform derivedin FIG. 9 according to one or more embodiments;

FIG. 11 illustrates the normalized signal of the triangular waveformshown in FIG. 10 together with the original speed signal and theoriginal direction signal shown in FIG. 5 according to one or moreembodiments;

FIG. 12 illustrates an output signal shown in FIG. 8 together with theoriginal speed and direction signals shown in FIG. 5 according to one ormore embodiments;

FIG. 13 illustrates angle sensor signal responses according to one ormore embodiments;

FIG. 14 illustrates absolute values of the sinusoidal waveforms shown inFIG. 13 according to one or more embodiments;

FIG. 15 illustrates a new angle signal waveform derived from the signalsshown in FIG. 14 according to one or more embodiments; and

FIG. 16 illustrates angle sensor signal responses, as shown in FIG. 13,according to one or more embodiments.

DETAILED DESCRIPTION

In the following, details are set forth to provide a more thoroughexplanation of the exemplary embodiments. However, it will be apparentto those skilled in the art that embodiments may be practiced withoutthese specific details. In other instances, well-known structures anddevices are shown in block diagram form or in a schematic view ratherthan in detail in order to avoid obscuring the embodiments. In addition,features of the different embodiments described hereinafter may becombined with each other, unless specifically noted otherwise.

Further, equivalent or like elements or elements with equivalent or likefunctionality are denoted in the following description with equivalentor like reference numerals. As the same or functionally equivalentelements are given the same reference numbers in the figures, a repeateddescription for elements provided with the same reference numbers may beomitted. Hence, descriptions provided for elements having the same orlike reference numbers are mutually exchangeable.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

In embodiments described herein or shown in the drawings, any directelectrical connection or coupling, i.e., any connection or couplingwithout additional intervening elements, may also be implemented by anindirect connection or coupling, i.e., a connection or coupling with oneor more additional intervening elements, or vice versa, as long as thegeneral purpose of the connection or coupling, for example, to transmita certain kind of signal or to transmit a certain kind of information,is essentially maintained. Features from different embodiments may becombined to form further embodiments. For example, variations ormodifications described with respect to one of the embodiments may alsobe applicable to other embodiments unless noted to the contrary.

Embodiments relate to sensors and sensor systems, and to obtaininginformation about sensors and sensor systems. A sensor may refer to acomponent which converts a physical quantity to be measured to anelectric signal, for example, a current signal or a voltage signal. Thephysical quantity may for example comprise a magnetic field, an electricfield, a pressure, a force, a current or a voltage, but is not limitedthereto. A sensor device, as described herein, may be an angle sensor, alinear position sensor, a speed sensor, motion sensor, and the like.

A magnetic field sensor, for example, includes one or more magneticfield sensor elements that measure one or more characteristics of amagnetic field (e.g., an amount of magnetic field flux density, a fieldstrength, a field angle, a field direction, a field orientation, etc.).The magnetic field may be produced by a magnet, a current-carryingconductor (e.g., a wire), the Earth, or other magnetic field source.Each magnetic field sensor element is configured to generate a sensorsignal (e.g., a voltage signal) in response to one or more magneticfields impinging on the sensor element. Thus, a sensor signal isindicative of the magnitude and/or the orientation of the magnetic fieldimpinging on the sensor element.

It will be appreciated that the terms “sensor” and “sensing element” maybe used interchangeably throughout this description, and the terms“sensor signal” and “measurement signal” may be used interchangeablythroughout this description.

Magnetic sensors include magnetoresistive sensors and Hall-effectsensors (Hall sensors), for example. Magnetoresistance is a property ofa material to change the value of its electrical resistance when anexternal magnetic field is applied to it. Some examples ofmagnetoresistive effects are Giant Magneto-Resistance (GMR), which is aquantum mechanical magnetoresistance effect observed in thin-filmstructures composed of alternating ferromagnetic and non-magneticconductive layers, Tunnel Magneto-Resistance (TMR), which is amagnetoresistive effect that occurs in a magnetic tunnel junction (MTJ),which is a component consisting of two ferromagnets separated by a thininsulator, or Anisotropic Magneto-Resistance (AMR), which is a propertyof a material in which a dependence of electrical resistance on theangle between the direction of electric current and direction ofmagnetization is observed. For example, in the case of AMR sensors, aresistance for an AMR sensor element changes according to a square of asine of an angle of the magnetic field component projected on a sensingaxis of the ARM sensor element.

The plurality of different magnetoresistive effects is commonlyabbreviated as xMR, wherein the “x” acts as a placeholder for thevarious magnetoresistive effects. xMR sensors can detect the orientationof an applied magnetic field by measuring sine and cosine anglecomponents with monolithically integrated magnetoresistive sensorelements.

Magnetoresistive sensor elements of such xMR sensors typically include aplurality of layers, of which at least one layer is a reference layerwith a reference magnetization (i.e., a reference direction). Thereference magnetization provides a sensing direction corresponding to asensing axis of the xMR sensor. Accordingly, if a magnetic fieldcomponent points exactly in the same direction as the referencedirection, a resistance of the xMR sensor element is at a maximum, and,if a magnetic field component points exactly in the opposite directionas the reference direction, the resistance of the xMR sensor element isat a minimum.

In some applications, an xMR sensor includes a plurality ofmagnetoresistive sensor elements, which have different referencemagnetizations. Examples of such applications, in which variousreference magnetizations are used, are angle sensors, compass sensors,or specific types of speed sensors (e.g., speed sensors in a bridgearrangement referred to as monocells).

By way of example, such magnetoresistive sensor elements are used inspeed, angle or rotational speed measuring apparatuses, in which magnetsmay be moved relative to an magnetoresistive sensor elements and hencethe magnetic field at the location of the magnetoresistive sensorelement changes in the case of movement, which, in turn, leads to ameasurable change in resistance. For the purposes of an angle sensor, amagnet or a magnet arrangement may be applied to a rotatable shaft andan xMR sensor may be arranged stationary in relation thereto.

A Hall effect sensor is a transducer that varies its output voltage(Hall voltage) in response to a magnetic field. It is based on the Halleffect which makes use of the Lorentz force. The Lorentz force deflectsmoving charges in the presence of a magnetic field which isperpendicular to the current flow through the sensor or Hall plate.Thereby a Hall plate can be a thin piece of semiconductor or metal. Thedeflection causes a charge separation which causes a Hall electricalfield. This electrical field acts on the charge in the oppositedirection with regard to the Lorentz Force. Both forces balance eachother and create a potential difference perpendicular to the directionof current flow. The potential difference can be measured as a Hallvoltage and varies in a linear relationship with the magnetic field forsmall values. Hall effect sensors can be used for proximity switching,positioning, speed detection, and current sensing applications.

In some examples, Hall sensor elements may be implemented as a verticalHall sensor elements. A vertical Hall sensor is a magnetic field sensorwhich is sensitive to a magnetic field component which extends parallelto their surface. This means they are sensitive to magnetic fieldsparallel, or in-plane, to the IC surface. The plane of sensitivity maybe referred to herein as a “sensitivity-axis” or “sensing axis” and eachsensing axis has a reference direction. For Hall sensor elements,voltage values output by the sensor elements change according to themagnetic field strength in the direction of the sensing axis.

In other examples, Hall sensor elements may be implemented as lateralHall sensor elements. A lateral Hall sensor is sensitive to a magneticfield component perpendicular to their surface. This means they aresensitive to magnetic fields vertical, or out-of-plane, to theintegrated circuit (IC) surface. The plane of sensitivity may bereferred to herein as a “sensitivity-axis” or “sensing axis” and eachsensing axis has a reference direction. For Hall sensor elements,voltage values output by the sensor elements change according to themagnetic field strength in the direction of the sensing axis.

According to one or more embodiments, a magnetic field sensor and asensor circuit may be both accommodated (i.e., integrated) in the samechip package (e.g., a plastic encapsulated package, such as leadedpackage or leadless package, or a surface mounted device (SMD)-package).This chip package may also be referred to as sensor package. The sensorpackage may be combined with a back bias magnet to form a sensor module,sensor device, or the like.

The sensor circuit may be referred to as a signal processing circuitand/or a signal conditioning circuit that receives one or more signals(i.e., sensor signals) from one or more magnetic field sensor elementsin the form of raw measurement data and derives, from the sensor signal,a measurement signal that represents the magnetic field. Signalconditioning, as used herein, refers to manipulating an analog signal insuch a way that the signal meets the requirements of a next stage forfurther processing. Signal conditioning may include converting fromanalog to digital (e.g., via an analog-to-digital converter),amplification, filtering, converting, biasing, range matching, isolationand any other processes required to make a sensor output suitable forprocessing after conditioning.

Thus, the sensor circuit may include an analog-to-digital converter(ADC) that converts the analog signal from the one or more sensorelements to a digital signal. The sensor circuit may also include adigital signal processor (DSP) that performs some processing on thedigital signal, to be discussed below. Therefore, the sensor package mayinclude a circuit that conditions and amplifies the small signal of themagnetic field sensor element via signal processing and/or conditioning.

A sensor device, as used herein, may refer to a device which includes asensor and sensor circuit as described above. A sensor device may beintegrated on a single semiconductor die (e.g., silicon die or chip),although, in other embodiments, a plurality of dies may be used forimplementing a sensor device. Thus, the sensor and the sensor circuitare disposed on either the same semiconductor die or on multiple dies inthe same package. For example, the sensor might be on one die and thesensor circuit on another die such that they are electrically connectedto each other within the package. In this case, the dies may becomprised of the same or different semiconductor materials, such as GaAsand Si, or the sensor might be sputtered to a ceramic or glass platelet,which is not a semiconductor.

FIG. 1 is a block diagram illustrating a magnetic speed sensor 100according to one or more embodiments. The magnetic speed sensor 100includes sensor elements L, C, and R that are configured to generate asensor signal in response to a magnetic field impinging thereon. Thesensor elements L, C, and R are configured to measure a same fieldcomponent (e.g., an x-component, a y-component, or a z-component) of amagnetic field according to their sensing axis. The sensor elements L,C, and R may be arranged such that sensor element L and sensor element Rare set apart from each other, for example, by a distance equal to halfa pitch of the poles or teeth of a target object (e.g., a magneticencoder wheel or a tooth and notch wheel), and the sensor element C isdisposed therebetween.

The magnetic speed sensor 100 also includes a sensor circuit 10 thatreceives the sensor signals from the sensor elements L, C, and R forprocessing and for generation of a speed output signal. The sensorcircuit 10 includes two signal paths: a speed signal path and adirection signal path. The signal on the speed signal path may be in aform of a sinusoidal (sine) waveform that represents a rotation of thetarget object, and the signal on the direction signal path may be asimilar waveform that is shifted 90° from the speed signal. That is, thedirection signal is a sinusoidal (cosine) waveform that represents arotation of the target object. It will be appreciated that while theexamples herein describe the sine waveform as being used as the speedsignal and the cosine waveform as being used as the direction signal,the opposite may also be true so long as the two signals are phaseshifted 90° from each other.

The speed signal path of the sensor circuit 10 may include combiningcircuitry 11 s that receives sensor signals from sensor elements L and Rand generates a differential measurement signal therefrom. For example,the combining circuitry 11 s may include one or more differentialamplifiers that outputs the difference between sensor elements L and R(e.g., L-R). The differential measurement signal of the speed signalpath may be represented as a sinusoidal (sine) signal and may bereferred to herein as a speed signal that corresponds a rotation of thetarget object. A differential measurement signal provides robustness tohomogenous external stray magnetic fields.

In addition, the speed signal path may include an ADC 12 s that convertsthe differential measurement signal of the speed signal path into adigital signal for further processing by a remaining portion of thesensor circuit 10.

It will be appreciated that other logic and circuitry other than or incombination with a differential amplifier may be used as the combiningcircuitry 11 s to generate the differential measurement signal, or othercombinations of sensor signals from sensor elements L, C, and R may beused to generate the speed signal. For example, the measurement signalmay be a differential measurement signal, derived from two sensorsignals using differential calculus.

Additionally, it will also be appreciated that combining circuitry 11 sis optional, and that one of the sensor signals from one of the sensorelements L, C or R may be used as a monocell and may be directly appliedto the ADC and used as the speed signal.

The direction signal path of the sensor circuit 10 may include combiningcircuitry 11 d that receives sensor signals from sensor elements L, C,and R and generates a differential measurement signal therefrom. Forexample, the combining circuitry 11 d may include one or moredifferential amplifiers that outputs the difference between sensorelements C and R (e.g., C-R). The differential measurement signal of thedirection signal path may be represented as a cosine signal and may bereferred to herein as a direction signal that corresponds a rotation ofthe target object. Thus, the direction signal is a similar waveform tothat of the speed signal, but is phase shifted 90° from the speedsignal.

In some cases, the direction signal may have a smaller extrema (i.e.,maximum and minimum) when compared to the speed signal. However, in thiscase, when the two signals are normalized to a common amplitude, it canbe seen that the direction signal is similar to the speed signal, butphase shifted by 90°.

Since the speed signal and the direction signal are phase shifted fromeach other by 90°, a direction of rotation of the target object can bedetermined therefrom based on whether the phase shift is a positive or anegative 90° (i.e., via the direction of the phase shift).

In addition, the direction signal path may include an ADC 12 d thatconverts the differential measurement signal of the direction signalpath into a digital signal for further processing by a remaining portionof the sensor circuit 10.

It will be appreciated that other logic and circuitry other than or incombination with a differential amplifier may be used as the combiningcircuitry 11 d to generate the differential measurement signal, or othercombinations of sensor signals from sensor elements L, C, and R may beused to generate the direction signal.

Additionally, it will also be appreciated that combining circuitry 11 dis optional, and that one of the sensor signals from one of the sensorelements L, C or R may be used as a monocell and may be directly appliedto the ADC and used as the direction signal. For example, if the sensorelement L is used as a monocell for generating the speed signal, sensorelement C may be used as a monocell for generating the direction signal.

The sensor circuit 10 further includes a signal conversion algorithmblock 13 that receives the speed signal and the direction signal forfurther processing. For example, the signal conversion algorithm block13 may include one or more processors and/or logic units that performsvarious signal conditioning functions, such as absolute signalconversion, normalization, linearization, and so forth. One or moresignal conditioning functions may be performed in combination with alookup table stored in memory 14. The output of the signal conversionalgorithm block 13 is provided a signal protocol block 15 that isconfigured to generate a speed pulse signal as an output signal. Each“block” may include one or more processors for processing one or moresignals.

FIG. 2A is an example of a sinusoidal waveform generated by a magneticspeed sensor according to one or more embodiments. FIG. 2B is a planview of a magnetic encoder wheel 20 that is configured to rotate aboutan axis according to one or more embodiments. In particular, FIG. 2Ashows a full revolution speed sensor signal response of one fullrevolution of the magnetic encoder wheel 20. The speed sensor signalresponse may be a sensor signal generated by a signal sensor element(e.g., L, C, or R) or may be a differential measurement signal describedabove.

A pole pair includes adjacent north and south poles on the encoderwheel, or adjacent tooth and notch on a toothed wheel (not shown).Typically, for speed applications, the number of pole pairs of thetarget wheel, which also corresponds to a number of teeth on a toothwheel) translates into a number of sine waveforms for a full revolutionof 360°. For this example, the magnetic encoder wheel 20 would include24 pole pairs, according to the sinusoidal waveform shown in FIG. 2A.However, FIG. 2B only shows a limited number of pole pairs (4) for thesimplicity of representation.

To measure a wheel speed (e.g., in an automotive application) theencoder wheel 20 is used in combination with the magnetic speed sensor100. The sensor 100 generates an output signal based on a sensedmagnetic field that oscillates between two extrema (e.g., a minimum andmaximum) in accordance with the rotation of the encoder wheel. A controlunit (e.g., an electronic control unit (ECU), including at least oneprocessor, is able to calculate a wheel-speed and an actual angle of therotating encoder wheel based on the output signals generated by thesensor circuit 10.

In view of the above, a measurement signal is a measurement of themagnetic field B sensed over time t by the magnetic speed sensor 100,and oscillates between the two extrema as the magnetic encoder rotates.Furthermore, the measurement signal may have an offset from an x-axis ina y-axis direction, and may further be normalized to a common amplitudeby processing performed by the sensor circuit 10.

The pulses of an output signal may be generated by signal protocol block15 upon the detection of a crossing of a switching point (i.e., aswitching threshold) of the measurement signal provided by the signalconversion algorithm block 13. The switching point, stored in memory 14(e.g., in a look-up table), is located between the minimum (min) and themaximum (max) of the magnetic field B.

Furthermore, the sensor circuit 10, for example, via the signalconversion algorithm block 13, may regularly and autonomously(re)calculate the switching point and self-calibrate the switching pointbased on an average of one or more minima and one or more maxima of themeasured magnetic field, or based on the calculated speed (e.g.,frequency) of one or more sensor signals or measurement signals.

For example, the switching point may be calculated as an average of themost recent minimum and maximum values of the measurement signal, andadjusted accordingly. Alternatively, the switching point may be adjustedbased on a value of the speed signal and determined from a look-up tablethat stores speed values and corresponding switching points. By adaptingthe switching point on a continual and dynamic basis, the accuracy ofthe switching point is maintained in a desired region in accordance withfast changes of the measurement signal and assures that a good jitterperformance is achieved.

FIG. 3A is a block diagram illustrating a magnetic angle sensor 300according to one or more embodiments. The magnetic speed sensor 300includes sensor elements X and Y that are configured to generate asensor signal in response to a magnetic field impinging thereon.

The sensor elements X and Y may be arranged such that sensor element Xand sensor element Y are set apart from each other by a predetermineddistance such that two sensor signals are generated that are phaseshifted from each other by 90°. In this case, the X sensor element andthe Y sensor element may be lateral Hall sensor elements such that thesensor element X is configured to sense the sine angle component (e.g.,x-component) of the magnetic field and the sensor element Y isconfigured to sense the cosine angle component (e.g., y-component) ofthe magnetic field.

Alternatively, sensor elements X and Y may each represent a resistorbridge each including four sensor elements (e.g., xMR sensor elements).In particular, a first resistor bridge X includes four sensor elements(e.g., xMR sensor elements) with different magnetization directions forderiving a sine angle component (e.g., x-component) of the magneticfield and a second resistor bridge Y includes four sensor elements(e.g., xMR sensor elements) with different magnetization directions forderiving a cosine angle component (e.g., y-component) of the magneticfield.

For example, FIG. 3B illustrates an example of a first resistor bridge Xthat generates sensor signal Sx and includes four xMR sensor elementsR1, R2, R3, and R4 with arrows provided to denote a direction of apinned-layer magnetization of each sensor element aligned in thex-direction. FIG. 3B further illustrates an example of a second resistorbridge Y that generates sensor signal Sy and includes four xMR sensorelements R5, R6, R7, and R8 with arrows provided to denote a directionof a pinned-layer magnetization of each sensor element aligned in they-direction.

Each sensor element of the first resistor bridge X is arranged on theangle sensor 300 at a substantially same position as a corresponding oneof the sensor elements of the second resistor bridge Y. Thus, eachresistor bridge outputs a sensor signal that is phase shifted from theother resistor bridge by 90 degrees.

It will be appreciated that other arrangements of sensor elements anduse of other types of sensor elements are possible, and are not limitedto the above examples, so long as the two measurement signals are phaseshifted 90° from each other.

The magnetic angle sensor 300 also includes a sensor circuit 30 thatreceives the sensor signals from the sensor elements X and Y forprocessing and for generation of an angle output signal. The sensorcircuit 30 includes two signal paths: an X signal path and a Y signalpath. The signal-X on the X signal path may be in a form of a sinusoidal(sine) waveform that represents an angular orientation of the targetobject, and the signal-Y on the Y signal path may be a similar waveformthat is shifted 90° from signal-X. That is, signal-Y is a sinusoidal(cosine) waveform that represents an angular orientation of the targetobject. It will be appreciated that while the examples herein describethe sine waveform as being used as signal-X and the cosine waveform asbeing used as signal-Y, the opposite may also be true so long as the twosignals are phase shifted 90° from each other.

Signal paths X and Y may include an ADC 31 x and an ADC 31 y,respectively, that convert the measurement signal of the respectivesignal path into a digital signal for further processing by a remainingportion of the sensor circuit 30.

In addition, a temperature compensation (TC), self-calibration, andfilter block 32 may receive each of the measurement signals X and Y, andperform one or more signal conditioning operations thereof beforeoutputting the measurement signals X and Y to signal conversionalgorithm block 33.

The signal conversion algorithm block 33 is configured to receivesignal-X and signal-Y for further processing. For example, the signalconversion algorithm block 33 may include one or more processors and/orlogic units that performs various signal conditioning functions, such asabsolute signal conversion, normalization, linearization, frequencyincrease, and so forth. One or more signal conditioning functions may beperformed in combination with a lookup table stored in memory 34. Theoutput of the signal conversion algorithm block 13 is provided an angleprotocol block 35 that is configured to generate an angle signal as anoutput signal. Each “block” may include one or more processors forprocessing one or more signals.

FIG. 4A is an example of a sinusoidal waveform generated by a magneticangle sensor according to one or more embodiments. FIG. 4B is a planview of a magnetic target 40, including a north pole and a south pole,that is configured to rotate about an axis according to one or moreembodiments. In particular, FIG. 4A shows a full revolution angle sensorsignal response of one full revolution of the magnetic target 40. Theangle sensor signal response may be a sensor signal generated by asensor element (e.g., resistor bridge X or resistor bridge Y), or acombination thereof. The magnetic target 40 may be a magnet, a magneticpill, a wheel, a shaft, and the like, but is not limited thereto.

To measure an angular position (e.g., in an automotive application) themagnetic target 40 is used in combination with the magnetic angle sensor300. The sensor 300 generates an output signal based on a sensedmagnetic field that oscillates between two extrema (e.g., a minimum andmaximum) in accordance with the orientation of the magnetic field as themagnetic target 40 rotates. A control unit (e.g., an electronic controlunit (ECU), including at least one processor, is able to calculate anabsolute angle of the magnetic target 40 based on the output signalsgenerated by the sensor circuit 30.

In view of the above, a measurement signal is a measurement of themagnetic field B sensed over time t by the magnetic angle sensor 300,and oscillates between the two extrema as the magnetic target rotates.Furthermore, the measurement signal may have an offset from an x-axis ina y-axis direction, and may further be normalized to a common amplitudeby processing performed by the sensor circuit 30.

In an anti-lock braking system (ABS), a magnetic sensor may be used inhill holder and parking assistant applications. High accuracy is desiredin both applications. However, with 30-60 poles on a standard ABS wheel,the resolution is too low and the ABS magnetic sensor is only capable todetect car movements in the range of 2 cm.

In transmission sensing, a magnetic sensor may also be used for ahillholder application. However, downsizing of the transmission unitscauses the distance between the pole wheel and the magnetic sensorincreases, since the magnetic sensor will be placed outside of thetransmission unit. This results in larger distances between magneticsensor and pole wheel. For such large distances, a strong magnetic fieldis required which can only be achieved by increasing (e.g., doubling)the pitch on the wheel. With a constant wheel diameter this causes areduction of the pole pairs (i.e., the sensor will generate half of thepulses). To compensate this behaviour without of the need of softwaremodifications, the transmission sensor should deliver at least doublethe number pulses.

Angle sensors typically used a combination of sine and cosine signals(i.e., 90° phase shifted signal) to determine the correct angleinformation based on trigonometric functions (e.g., a tan). An efficientway to do this on an application specific integrated circuit (ASIC)level is by using the so-called COordinate Rotation DIgital Computer(CORDIC) function (also known as Volder's algorithm). The CORDICfunction is a simple and efficient algorithm to calculate hyperbolic andtrigonometric functions, typically converging with one digit (or bit)per iteration.

The operation of the signal conversion algorithm block 13 and signalconversion algorithm block 33 will now be described in further detail.While the signal conversion algorithm block 13 and the signal conversionalgorithm block 33 are described above in different applications (e.g.,speed sensing and angle sensing), similar concepts can be applied toboth. For example, both signal conversion algorithm blocks 13 and 33 areconfigured to receive two measurement signals (e.g., sine and cosine)that are phase shifted from each other by 90°. In both applications, thesignal conversion algorithm blocks 13 and 33 are configured to increasea number of zero-crossings or a frequency of a measurement signal basedon the two phase shifted sensor signals.

With respect to a speed sensing application, it may be desired toincrease the number of zero crossings per revolution. For example, anABS sensor or a transmissions sensor may deliver a protocol (e.g., agenerated pulse) on every zero crossing of a measurement signal. If thenumber of zero crossings per revolution is increased, then the number ofpulses per revolution can also be increased.

FIG. 5 illustrates sinusoidal waveforms of a speed signal and adirection signal for one pole pair (i.e., 6°) generated by a speedsensor according to one or more embodiments. In particular, FIG. 5 showsan example of a speed signal and a direction signal that are input tothe signal conversion algorithm block 13 of FIG. 1. The speed anddirection channel signals are phase shifted by a half period.

The x-axis of FIG. 5 is shown in degrees)(°, whereas the y-axis shows anormalized value corresponding to milliteslas (mT). Assuming to have areference pole wheel with 60 pole pairs over 360° revolution, each polepair represents 6° of a full revolution. In its current form, andassuming one pulse is generated at the speed pulse generation block 15on each zero crossing in the speed path, the speed signal results in twopulses per 6° (e.g., one pulse at 0° and the other pulse at 3°).

It is noted that, the signals shown in FIG. 5 are normalized to a commonamplitude for simplification. In a typical application, an amplitude ofthe speed signal may be 10 mT and an amplitude of the direction signalmay be 3 mT. Signal conditioning may be applied by the signal conversionalgorithm block 13 to normalize both signals or a difference in theamplitude of the signals should be considered in the calculationspresented below. Thus, for the simplicity of explanation, it will beassumed that the speed signal and the direction signal are normalized toa common amplitude hereafter, as shown in FIG. 5, and the signalconversion algorithm block 13 continues to perform post-processing onthe normalized signals.

FIG. 6 illustrates absolute values of the sinusoidal waveforms shown inFIG. 5 according to one or more embodiments. In particular, the signalconversion algorithm block 13 is configured to generate the signalsabs(speed) and abs(direction) derived from the absolute value of each ofthe normalized speed signal and the normalized direction signal shown inFIG. 5, respectively.

FIG. 7 illustrates a new speed signal waveform derived from the signalsshown in FIG. 6 according to one or more embodiments. In particular, thenew speed signal is a triangular shaped signal with an increased numberof zero crossings. The new speed signal may be referred to as speed(L),corresponding to the lower portion of abs(speed) and abs(direction),whereas the remaining portion of the two waveforms of FIG. 7 may formanother signal, speed(U), corresponding to the upper portion ofabs(speed) and abs(direction).

As shown in FIG. 7, the signal conversion algorithm block 13 isconfigured to extract the signal speed(L) from the signals abs(speed)and abs(direction) that intersect with each other. For example, thesignal conversion algorithm block 13 may apply a non-lineal function orcalculation to the signals abs(speed) and abs(direction) to derivesignal speed(L). The non-linear function may be used, for example, to“track” or “reproduce” in some way the lesser of the signals abs(speed)and abs(direction) to generate the triangular waveform, speed(L). Thatis, the abs(speed) and abs(direction) signals may be compared to eachother, and smaller of the two signals may be used by the signalconversion algorithm block 13 for generating the triangular waveform,speed(L). The remaining portions of the signals abs(speed) andabs(direction) that are not used to form signal speed(L) may beextracted to form signal speed(U).

The rule for the non-linear function in this case to derive signalspeed(L) may be described, in the context of FIG. 5, as follows:

Use the speed signal, when direction>speed>0; and

Use the direction signal, when speed>direction>0.

Alternatively, the rule for the non-linear function in this case toderive signal speed(L) may be described, in the context of FIG. 6, asfollows:

Use the signal abs(speed), when abs(direction)>abs(speed); and

Use the signal abs(direction), when abs(speed)>abs(direction).

Thus, the function applied to the abs(speed) and abs(direction) signalscan be summarized as follows: as long as the direction signal is largerthan the speed signal follow the speed path; and once the speed signalis larger than the direction signal, follow the direction path.Depending on the circumstances, the function applied to the abs(speed)and abs(direction) signals may be chosen as a linear function, anon-linear function, or any other suitable function.

Looking at FIG. 7, a person of skill in the art will recognize that itmay be of interest for suitable functions to substantially follow one ofthe abs(speed) and the abs(direction) signals until a turning point ofthe one of the abs signals is reached. From this first turning point,the function substantially follows the other one of the abs(speed)signal and the abs(direction) signal until a second turning point of theother one of the abs signals is reached. From this second turning pointsuitable functions would substantially follow the second abs signaluntil the third turning point is reached. In other words, suitablefunctions may change which abs signal is substantially being trackedfrom one turning point to the next.

Various functions may be used to achieve the same or similar result. Forexample, an interpolation function may be applied to the abs(speed) andabs(direction) signals, such that various points of the lower of the twosignals are detected, and the interpolation function (e.g., splineinterpolation) may be applied to the sampled values to generate anoptimal waveform, e.g., speed(L), with regards to duty cycle.Alternatively, a linear fit may be applied to the sampled values togenerate a linearized waveform, e.g., speed(L).

While the waveform speed(L) is illustrated as a triangular signal (orcurved triangle), the embodiments described herein are not limitedthereto, and other shaped waveforms are possible, for example, tocompensate for phase differences. Thus, the signal(s) generated by thesignal conversion algorithm block 13 by applying one or more functionsdescribed above may generally be referred to as a converted signal.

Alternatively, signal conversion algorithm block 13 may be configured toextract the signal speed(U) from the signals abs(speed) andabs(direction) in a similar manner. For example, a non-linear functionmay be applied to the abs(speed) and abs(direction) signals such that:as long as the direction signal is larger than the speed signal followthe direction path; and once the speed signal is larger than thedirection signal, follow the speed path. Thus, a triangular waveform,speed(U), may be generated by applying similar principles above.However, extracting the signal speed(L) may be more desirable since thelower portion of the signals abs(speed) and abs(direction) is naturallyakin to a triangular shaped waveform and require less processing andestimating.

FIG. 8 illustrates a normalized signal of the triangular waveform shownin FIG. 7 according to one or more embodiments. In particular, signalspeed(out1) is a normalization of the triangular shaped signal,speed(L), and is provided to the speed pulse generation block 15 togenerate the pulsed output signal based on one or more switchingthresholds.

If the signal speed(out1) is compared with the initial speed signal, itcan be seen that the number of zero crossings is increased from two perpole pair to eight per pole pair. Thus, if delivering one pulse on everyrising edge or on every falling edge of signal speed(out1), the speedpulse generation block 15 would provide four pulses per pole pair.Moreover, if delivering one pulse on both rising edges and falling edgesof signal speed(out1), the speed pulse generation block 15 would provideeight pulses per pole pair.

Due to slightly non-linearities of the sine and cosine function, thezero crossings may no longer be well distributed around the 6° of a polepair. That is, the duty cycle may be irregular and may cause performanceissues. Wave shaping or adjustment of the switching threshold may beapplied to compensate for this effect.

For example, as mentioned above, wave shaping may be performed on signalspeed(L) to convert the signal into a more ideal triangular waveform to,for example, linearize the signal. Alternatively, the wave shapingprocessing may be applied to signal speed(out1) on an ongoing, real-timebasis for similar reasons. In either case, a single switching threshold(e.g., at zero) may be used by the speed pulse generation block 15 togenerate the pulsed output signal, and this switching threshold may notneed adjusting due to the wave shaping performed on signal speed(out1).

Alternatively, the switching threshold may be adjusted on a dynamic,real-time basis to compensate for irregularities of the duty cycle insignal speed(out1). In particular, a look up table may be used, anddepending on an input value of the speed signal (or direction signal)from FIG. 5, the switching threshold applied by the speed pulsegeneration block 15 for the signal speed(out1) may be adjusted above orbelow zero. For example, the look up table may map different speedvalues (or frequency values) to different switching thresholds, and thespeed pulse generation block 15 may selectively apply a switchingthreshold that corresponds to a current speed value or frequency valuesuch that the switching threshold is adjusted to compensate for anyirregularities.

In addition, two switching thresholds may be applied and adjusted usinga similar principle. For example, a upper switching threshold,maintained above zero, may be used for generating a pulse at a risingedge crossing of the signal speed(out1), the pulse being triggered whenthe signal speed(out1) crosses the upper switching threshold on a risingedge. Also, a lower switching threshold, maintained below zero, may beused for generating a pulse at a falling edge crossing of the signalspeed(out1), the pulse being triggered when the signal speed(out1)crosses the lower switching threshold on a falling edge. Accordingly,one or more look up tables may map different speed values (or frequencyvalues) to both an upper switching threshold and a lower switchingthreshold, and each of the upper switching threshold and the lowerswitching threshold may be adjusted based on a current speed value orfrequency value to compensate for any irregularities.

Alternatively, instead of using a speed value of the speed signal toadjust one or both of the switching thresholds, a self-learningalgorithm may be applied. For example, the dual thresholds may beadjusted by trial-and-error until a desired/correct duty cycle isachieved at the output.

The above embodiments demonstrate that a number of zero crossings perpole pair can be increased from two to eight. In addition, the followingembodiments demonstrate that the number of zero crossings per pole paircan be increased from two to sixteen.

Referring back to FIG. 7, signals speed(L) and speed(U) were generatedby the signal conversion algorithm block 13 from the signals illustratedin FIG. 6. After signals speed(L) and speed(U) are generated, the twosignals can be normalized, as shown in FIG. 9. Thus, FIG. 9 illustratesnormalized speed signals (i.e., speed(L_norm) and speed(U_norm)) derivedfrom signals speed(L) and speed(U) shown in FIG. 7.

Once speed(L) and speed(U) are normalized, the signal conversionalgorithm block 13 is configured to extract a lower portion of the twointersecting signals, signals speed(L_norm) and speed(U_norm), in asimilar manner that was used to extract or generate signal speed(L) asdescribed with respect to FIG. 7. For example, the signal conversionalgorithm block 13 may be configured to compare the signalsspeed(L_norm) and speed(U_norm) shown in FIG. 9 to each other. Thesmaller of the two signals is used to generate a triangular waveform,speed(out2), shown in FIG. 10, that is used for further signalprocessing.

While the waveform speed(out2) is illustrated as a triangular signal (orcurved triangle), the embodiments described herein are not limitedthereto, and other shaped waveforms are possible, for example, tocompensate for phase differences. Thus, the signal(s) generated by thesignal conversion algorithm block 13 by applying one or more functionsdescribed above may generally be referred to as a converted signal.

The signal conversion algorithm block 13 may apply a non-lineal functionor calculation to the speed(L_norm) and speed(U_norm) to derive thelower triangular waverform. The non-linear function may be used, forexample, to “track” or “reproduce” in some way the lesser of the signalsspeed(L_norm) and speed(U_norm) to generate the triangular waveform. Therule for the non-linear function in this case to derive the triangularwaveform may be described, in the context of FIG. 9, as follows:

Use the signal speed(L_norm), when speed(U_norm)>speed(L_norm); and

Use the signal speed(U_norm), when speed(L_norm)>speed(U_norm).

FIG. 10 illustrates a normalized signal of the triangular waveformderived in FIG. 9 according to one or more embodiments. FIG. 11illustrates the normalized signal of the triangular waveform of FIG. 10together with the original speed signal and the original directionsignal shown in FIG. 5. In particular, signal speed(out2) is anormalization of the triangular shaped signal formed by the lowerportion of and extracted from signals speed(L_norm) and speed(U_norm),and is provided to the speed pulse generation block 15 to generate thepulsed output signal based on one or more switching thresholds. As canbe observed from FIG. 10 and FIG. 11, the number of zero crossings isfurther increased to sixteen zero crossings per pole p air.

However, it can also be seen that the signal speed(out2) may also havesome unwanted phase shifts and an irregular duty cycle resulting inhigher period jitter. This problem of inaccuracy could then becompensated again by similar methods described above that were used tocompensate for irregularities of the duty cycle in signal speed(out1).In particular, wave shaping to an ideal triangular waveform or anadjustment of one or more switching thresholds based on the speed and/ordirection signal may be applied to compensate for this effect.

By using the approaches described above to generate the new outputsignals speed(out1) and speed(out2), the new output signals speed(out1)and speed(out2) can no longer be used for rotation direction detectionusing traditional direction detection concepts. One solution may be touse the original speed and direction signals shown in FIG. 5 incombination with one of the new output signals speed(out1) orspeed(out2) for rotation direction detection. Since similar principlesapply when using signals speed(out1) or speed(out2) for rotationdirection detection, the procedure will be described only in referenceto signal speed(out1).

FIG. 12 illustrates the output signal, speed(out1), shown in FIG. 8together with the original speed and direction signals shown in FIG. 5.Rotation direction detection may be performed by the speed pulsegeneration block 15 by evaluation the original speed and directionsignals on every zero crossing of the output signal, speed(out1). Achange of rotation direction can be detected by comparing the speed anddirection signal on every zero crossing of the output signal,speed(out1). If the values of both the speed and direction signalsremain the same when compared to last sampling, a change of rotationdirection is detected. However, if at least one of the values of thespeed or direction signals has changed, then no change of rotationdirection occurred.

For example, the speed pulse generation block 15 may be configured totake a sample of the values of the speed and direction signals at afirst zero-crossing of speed(out1), store the values, and take a sampleof the values of the speed and direction signals at the next (second)zero-crossing of speed(out1), store the values, and compare these valueswith the previously stored values. If at least one of the valueschanges, the direction of rotation has remained the same. If both valuesremain the same compared to the previously stored values, a change inrotation direction has occurred and is detected.

As noted above, rotation direction detection may also be performed usingspeed(out2) by simply replacing speed(out1) with speed(out2) in theabove description.

For an angle sensor application, a combination of a sine measurementsignal and a cosine measurement signal are used in order to provideunambiguous angle information. FIG. 13 illustrates angle sensor signalresponses according to one or more embodiments. In particular, FIG. 13shows basic raw data signals generated by the X sensor elements (i.e.,the sine measurement signal X) and by the Y sensor elements (i.e., thecosine measurement signal Y). Signal X and Y are input to the signalconversion algorithm block 33 for further processing (e.g., absolutesignal conversion, normalization, linearization, and so forth).

FIG. 14 illustrates absolute values of the sinusoidal waveforms shown inFIG. 13 according to one or more embodiments. In particular, the signalconversion algorithm block 33 receives signals X and Y, and applies anabsolute signal conversion thereto to generate signals abs(X) andabs(Y), respectively.

Essentially, the signals illustrated in FIGS. 13 and 14 are identical tothe curves shown in FIGS. 5 and 6, respectively, not taking into accountthe different x-axis scaling. Accordingly, further processing may beperformed on signals abs(X) and abs(Y) by the signal conversionalgorithm block 33 according to the principles described in reference toFIGS. 7-11. As a result, the concepts described in detail above, can beapplied to an angle sensor signal response.

First, the so-called X and Y components (respectively sine and cosinesignals) are translated to absolute signals by the signal conversionalgorithm block 33, as shown in FIG. 14.

Second, as shown in FIG. 15, the absolute X and Y components arecompared to each other by the signal conversion algorithm block 33 toextract a lower portion thereof in order to generate signal ang(L).Here, the smaller signal of the two X and Y signals is used for furtherpost processing. The result is a triangular waveform as highlighted inFIG. 15 as the dashed line, which represents the new signal, ang(L).Again, this is identical to the steps described previously on FIGS. 5-8.

The rule for the non-linear function in this case to derive signalang(L) may be described, in the context of FIG. 15, as follows:

Use the signal abs(X), when abs(Y)>abs(X); and Use the signal abs(Y),when abs(X)>abs(Y).

Thus, only a simple “greater than” condition algorithm is required persignal. In the alternative, it will be appreciated that a “lesser than”condition algorithm may also be used here, and also in the speed sensingapplication.

Third, the linearized triangular waveform, ang(L), can now be furtherpost-processed and ultimately used by the angle protocol block 35 tocalculate absolute angle data. For instance, a simple signalnormalization and lookup table data quantization could be applied toobtain the angle information.

While the waveform ang(L) is illustrated as a triangular signal (orcurved triangle), the embodiments described herein are not limitedthereto, and other shaped waveforms are possible, for example, tocompensate for phase differences. Thus, the signal(s) generated by thesignal conversion algorithm block 33 by applying one or more functionsdescribed above may generally be referred to as a converted signal.

FIG. 16 illustrates angle sensor signal responses, as shown in FIG. 13,according to one or more embodiments. In particular, signals X and Y maybe used to obtain correct 360° angle information due to a loss of thisinformation during the conversion of the angle sensor signal responsesinto signal ang(L). This loss of information can be observed in FIG. 15where the signal ang(L) is repetitive from 180° onwards. In order toobtain correct 360° angle information, the original X and Y signals canbe used.

In FIG. 16, a possible algorithm applied by the angle protocol block 35is shown for obtaining the full 360° angle information. For instance, asimple sign check on the X-signal component is sufficient to detect thecorrect angle range. In other words, if the X-signal is positive, theangle is in the range of 0 to 180°, and, if the X-signal is negative,the angle is in the range of 180° to 360°. Of course, the Y-signal maybe used instead, or even both X and Y-signals can be taken into accountto detect the correct angle information. For example, if the Y-signal ispositive, the angle is in the range of 0 to 90° or 270 to 360°, and, ifthe Y-signal is negative, the angle is in the range of 90 to 270°.

The signal conversion algorithm applied by the signal conversionalgorithm block 33 may be used as a replacement or as a redundancy checkof the CORDIC function used by traditional angle sensors.

First, the signal conversion algorithm described herein may be used as afundamentally different method to calculate angle data. Thus, ifredundancy is of interest due to functional safety requirements, thesignal conversion algorithm may be used to as a separate, redundantcalculation to verify whether the CORDIC calculation is workingcorrectly.

Second, compared to the CORDIC calculation, this method may poseadditional advantages such as low latency or additional flexibility interms of angle accuracy over frequency.

In view of the above, a signal conversion algorithm may be applied toboth speed sensing and angle sensing applications in order to increasethe number of zero crossings of the measurement signal. Accordingly, theaccuracy of each sensing application may be improved, while allowing thestructural constraints of the overall system (e.g., size, and/orplacement of the target object with respect to the sensor, including airgap) to be relaxed. Offering an algorithm to dynamically increase theresolution offers the flexibility to for instance use a wheel with halfthe pole numbers, while doubling the number of zero crossings on thechip end to provide the same resolution as a wheel with the full numberof poles.

While the above embodiments are described in the context of detecting awheel or camshaft speed or angle, the sensor may be used to detect therotation speed or angle of any rotating member or object that createssinusoidal variations in a magnetic field as it rotates and that may besensed by a sensor. For example, a combination of a ferrous wheel and aback bias magnet may be used to generate a time varying magnetic field.Alternatively, an active encoder wheel (without a back bias magnetic)may be used to generate a time varying magnetic field.

Further, while various embodiments have been described, it will beapparent to those of ordinary skill in the art that many moreembodiments and implementations are possible within the scope of thedisclosure. Accordingly, the invention is not to be restricted except inlight of the attached claims and their equivalents. With regard to thevarious functions performed by the components or structures describedabove (assemblies, devices, circuits, systems, etc.), the terms(including a reference to a “means”) used to describe such componentsare intended to correspond, unless otherwise indicated, to any componentor structure that performs the specified function of the describedcomponent (i.e., that is functionally equivalent), even if notstructurally equivalent to the disclosed structure that performs thefunction in the exemplary implementations of the invention illustratedherein.

Furthermore, the following claims are hereby incorporated into thedetailed description, where each claim may stand on its own as aseparate example embodiment. While each claim may stand on its own as aseparate example embodiment, it is to be noted that—although a dependentclaim may refer in the claims to a specific combination with one or moreother claims—other example embodiments may also include a combination ofthe dependent claim with the subject matter of each other dependent orindependent claim. Such combinations are proposed herein unless it isstated that a specific combination is not intended. Furthermore, it isintended to include also features of a claim to any other independentclaim even if this claim is not directly made dependent to theindependent claim.

It is further to be noted that methods disclosed in the specification orin the claims may be implemented by a device having means for performingeach of the respective acts of these methods.

Further, it is to be understood that the disclosure of multiple acts orfunctions disclosed in the specification or claims may not be construedas to be within the specific order. Therefore, the disclosure ofmultiple acts or functions will not limit these to a particular orderunless such acts or functions are not interchangeable for technicalreasons. Furthermore, in some embodiments a single act may include ormay be broken into multiple sub acts. Such sub acts may be included andpart of the disclosure of this single act unless explicitly excluded.

The techniques described in this disclosure may be implemented, at leastin part, in hardware, software, firmware, or any combination thereof.For example, various aspects of the described techniques may beimplemented within one or more processors, including one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), or any other equivalent integrated ordiscrete logic circuitry, as well as any combinations of suchcomponents. The term “processor” or “processing circuitry” may generallyrefer to any of the foregoing logic circuitry, alone or in combinationwith other logic circuitry, or any other equivalent circuitry. A controlunit including hardware may also perform one or more of the techniquesof this disclosure. Such hardware, software, and firmware may beimplemented within the same device or within separate devices to supportthe various techniques described in this disclosure.

Although various exemplary embodiments have been disclosed, it will beapparent to those skilled in the art that various changes andmodifications can be made which will achieve some of the advantages ofthe concepts disclosed herein without departing from the spirit andscope of the invention. It will be obvious to those reasonably skilledin the art that other components performing the same functions may besuitably substituted. It is to be understood that other embodiments maybe utilized and structural or logical changes may be made withoutdeparting from the scope of the present invention. It should bementioned that features explained with reference to a specific figuremay be combined with features of other figures, even in those notexplicitly mentioned. Such modifications to the general inventiveconcept are intended to be covered by the appended claims and theirlegal equivalents.

What is claimed is:
 1. A magnetic sensor configured to measure amagnetic field whose magnitude oscillates between a first extrema and asecond extrema, the magnetic sensor comprising: a plurality of magneticfield sensor elements, each configured to generate a sensor signal inresponse to the magnetic field impinging thereon, wherein the pluralityof sensor elements are grouped into a first group from which a firstmeasurement signal is derived and a second group from which a secondmeasurement signal is derived, the first measurement signal and thesecond measurement signal having a phase difference based on differentphases; and a sensor circuit configured to receive the first measurementsignal and the second measurement signal, and apply a signal conversionalgorithm thereto to generate a converted measurement signal having anincreased frequency with respect to a frequency of the first measurementsignal and the second measurement signal.
 2. The magnetic sensor ofclaim 1, wherein: the sensor circuit is configured to apply an absolutevalue algorithm to both of the first measurement signal and the secondmeasurement signal in order to generate a first absolute value signal ofthe first measurement signal and a second absolute value signal of thesecond measurement signal, respectively, and apply a function to thefirst absolute value signal and the second absolute value signal toderive the converted measurement signal.
 3. The magnetic sensor of claim2, wherein, when generating the converted measurement signal, the firstmeasurement signal and the second measurement signal are normalized to acommon amplitude.
 4. The magnetic sensor of claim 2, wherein: thefunction includes continuously comparing the first absolute value signalwith the second absolute value signal over time, and generating theconverted measurement signal as the lesser of the first absolute valuesignal and the second absolute value signal based on the continuouscomparison.
 5. The magnetic sensor of claim 1, wherein: the sensorcircuit is configured to apply an absolute value algorithm to both ofthe first measurement signal and the second measurement signal in orderto generate a first absolute value signal of the first measurementsignal and a second absolute value signal of the second measurementsignal, respectively, and generate the converted measurement signal thatrepresents a lesser of the first absolute value signal and the secondabsolute value signal.
 6. The magnetic sensor of claim 1, wherein: thesensor circuit is configured to shape the converted measurement signalinto an optimal converted measurement signal.
 7. The magnetic sensor ofclaim 1, wherein: the sensor circuit is configured to apply an absolutevalue algorithm to both of the first measurement signal and the secondmeasurement signal in order to generate a first absolute value signal ofthe first measurement signal and a second absolute value signal of thesecond measurement signal, respectively, normalize the first absolutevalue signal and the second absolute value signal to a common amplitude,and generate the converted measurement signal, the converted measurementsignal representing a lesser of the normalized first absolute valuesignal and the normalized second absolute value signal.
 8. The magneticsensor of claim 1, wherein: the sensor circuit is configured to comparethe converted measurement signal to at least one switching threshold,and generate a pulsed output signal based on the converted measurementsignal crossing the at least one switching threshold, wherein the sensorcircuit is further configured to adjust the at least one switchingthreshold based on a frequency of the first measurement signal and thesecond measurement signal.
 9. The magnetic sensor of claim 1, whereinthe sensor circuit is further configured to: detect threshold crossingsof the converted measurement signal at at least one switching threshold;store a value of the first measurement signal and a value of the secondmeasurement signal at the threshold crossings; compare a current valueof the first measurement signal and a current value of the secondmeasurement signal with a previous value of the first measurement signaland a previous value of the second measurement signal, respectively; anddetect a change in rotation direction of the magnetic field based on acondition that the current value of the first measurement signal is thesame as the previous value of the first measurement signal and on acondition the current value of the second measurement signal is the sameas the previous value of the second measurement signal.
 10. The magneticsensor of claim 1, wherein: the sensor circuit is configured todetermine whether the first measurement signal is positive or negative,and determine an angle range of the converted measurement signal basedon whether the first measurement signal is positive or negative.
 11. Themagnetic sensor of claim 4, wherein the converted measurement signal isa waveform that tracks the first absolute value signal, on a conditionthat the first absolute value signal is less than the second absolutevalue signal, and tracks the second absolute value signal, on acondition that the second absolute value signal is less than the firstabsolute value signal.
 12. The magnetic sensor of claim 5, wherein theconverted measurement signal is a waveform that tracks the firstabsolute value signal, on a condition that the first absolute valuesignal is less than the second absolute value signal, and tracks thesecond absolute value signal, on a condition that the second absolutevalue signal is less than the first absolute value signal.
 13. Themagnetic sensor of claim 7, wherein the converted measurement signal isa waveform that tracks the first absolute value signal, on a conditionthat the first absolute value signal is less than the second absolutevalue signal, and tracks the second absolute value signal, on acondition that the second absolute value signal is less than the firstabsolute value signal.
 14. The magnetic sensor of claim 1, wherein: thefirst measurement signal, the second measurement signal, and theconverted measurement signal are analog signals, and the sensor circuitis configured to generate the converted measurement signal from thefirst measurement signal and the second measurement signal in an analogsignal processing domain.
 15. The magnetic sensor of claim 2, wherein:the function includes continuously comparing the first absolute valuesignal with the second absolute value signal over time, and generatingthe converted measurement signal as the greater of the first absolutevalue signal and the second absolute value signal based on thecontinuous comparison.
 16. The magnetic sensor of claim 1, wherein: thesensor circuit is configured to apply an absolute value algorithm toboth of the first measurement signal and the second measurement signalin order to generate a first absolute value signal of the firstmeasurement signal and a second absolute value signal of the secondmeasurement signal, respectively, and generate the converted measurementsignal that represents a greater of the first absolute value signal andthe second absolute value signal.
 17. The magnetic sensor of claim 1,wherein: the sensor circuit is configured to apply an absolute valuealgorithm to both of the first measurement signal and the secondmeasurement signal in order to generate a first absolute value signal ofthe first measurement signal and a second absolute value signal of thesecond measurement signal, respectively, normalize the first absolutevalue signal and the second absolute value signal to a common amplitude,and generate the converted measurement signal, the converted measurementsignal representing a greater of the normalized first absolute valuesignal and the normalized second absolute value signal.
 18. A method ofmeasuring a magnetic field whose magnitude oscillates between a firstextrema and a second extrema, the method comprising: generating a firstmeasurement signal representing the measured magnetic field; generatinga second measurement signal representing the measured magnetic field,wherein the first measurement signal and the second measurement signalhave a phase difference based on different phases; and applying a signalconversion algorithm to the first measurement signal and the secondmeasurement signal in order to generate a converted measurement signalhaving an increased frequency with respect to a frequency of the firstmeasurement signal and the second measurement signal.
 19. The method ofclaim 18, further comprising: applying an absolute value algorithm toboth of the first measurement signal and the second measurement signalin order to generate a first absolute value signal of the firstmeasurement signal and a second absolute value signal of the secondmeasurement signal, respectively; and applying a function to the firstabsolute value signal and the second absolute value signal to derive theconverted measurement signal.
 20. The method of claim 19, wherein, whengenerating the converted measurement signal, the first measurementsignal and the second measurement signal are normalized to a commonamplitude.
 21. The method of claim 19, wherein applying the functioncomprises: continuously comparing the first absolute value signal withthe second absolute value signal over time; and generating the convertedmeasurement signal as the lesser of the first absolute value signal andthe second absolute value signal based on the continuous comparison. 22.The method of claim 18, further comprising: applying an absolute valuealgorithm to both of the first measurement signal and the secondmeasurement signal in order to generate a first absolute value signal ofthe first measurement signal and a second absolute value signal of thesecond measurement signal, respectively; and generating the convertedmeasurement signal that represents a lesser of the first absolute valuesignal and the second absolute value signal.
 23. The method of claim 18,further comprising: shaping the converted measurement signal into anoptimal converted measurement signal.
 24. The method of claim 18,further comprising: applying an absolute value algorithm to both of thefirst measurement signal and the second measurement signal in order togenerate a first absolute value signal of the first measurement signaland a second absolute value signal of the second measurement signal,respectively; normalizing the first absolute value signal and the secondabsolute value signal to a common amplitude; and generating theconverted measurement signal, the converted measurement signalrepresenting a lesser of the normalized first absolute value signal andthe normalized second absolute value signal.
 25. The method of claim 18,further comprising: comparing the converted measurement signal to atleast one switching threshold; generating a pulsed output signal basedon the converted measurement signal crossing the at least one switchingthreshold; and adjusting the at least one switching threshold based on afrequency of the first measurement signal and the second measurementsignal.
 26. The method of claim 18, further comprising: detectingthreshold crossings of the converted measurement signal at at least oneswitching threshold; storing a value of the first measurement signal anda value of the second measurement signal at the threshold crossings;comparing a current value of the first measurement signal with aprevious value of the first measurement signal; comparing a currentvalue of the second measurement signal with a previous value of thesecond measurement signal; and detecting a change in rotation directionof the magnetic field based on a condition that the current value of thefirst measurement signal is the same as the previous value of the firstmeasurement signal and on a condition the current value of the secondmeasurement signal is the same as the previous value of the secondmeasurement signal.
 27. The method of claim 18, further comprising:determining whether the first measurement signal is positive ornegative; and determining an angle range of the converted measurementsignal based on whether the first measurement signal is positive ornegative.
 28. The method of claim 21, wherein the converted measurementsignal is a waveform that tracks the first absolute value signal, on acondition that the first absolute value signal is less than the secondabsolute value signal, and tracks the second absolute value signal, on acondition that the second absolute value signal is less than the firstabsolute value signal.
 29. The method of claim 22, wherein the convertedmeasurement signal is a waveform that tracks the first absolute valuesignal, on a condition that the first absolute value signal is less thanthe second absolute value signal, and tracks the second absolute valuesignal, on a condition that the second absolute value signal is lessthan the first absolute value signal.
 30. The method of claim 24,wherein the converted measurement signal is a waveform that tracks thefirst absolute value signal, on a condition that the first absolutevalue signal is less than the second absolute value signal, and tracksthe second absolute value signal, on a condition that the secondabsolute value signal is less than the first absolute value signal. 31.The method of claim 18, wherein: the first measurement signal, thesecond measurement signal, and the converted measurement signal areanalog signals, and applying a signal conversion algorithm is performedin an analog signal processing domain.
 32. The method of claim 19,wherein applying the function comprises: continuously comparing thefirst absolute value signal with the second absolute value signal overtime; and generating the converted measurement signal as the greater ofthe first absolute value signal and the second absolute value signalbased on the continuous comparison.